Personally, I suggest Digest::SHA rather than SHA1. SHA-1 will be superceded by 2010 at the latest, so you may want to be ready to implement SHA-256 or better with Digest::SHA. You may also want to look at the test data available at http://www.nsrl.nist.gov/testdata/

I found an evolved version of my SHA subroutine at:
http://mail-archives.apache.org/mod_mbox/spamassassin-commits/200407.mbox/%3C20040701190945.25657.qmail@minotaur.apache.org%3E
This one will also use Digest::SHA1 optionally if I read correctly, with 40X higher speed (!?).

I played around with Perlshop 3.2 in the late nineties, customizing it for selling aerial photos searchable on maps, or in tables. This museum piece sleeps at:
http://afoto.com/hildebilde/index.htm

Had a lot of fun making it bilingual.

Development of Perlshop continues at a good clip in version 4, with some nice features added while remaining effable for a neophyte like myself. This is the one that gave me the SHA error initially, but seems stable with the alternative routine.

It would be interesting to compare the speed with, and without Digest::SHA1 under load.